Bias and limits of agreement of Nexfin recorded cardiac output compared with LiDCOplus [ Time Frame: During anaesthesia period of surgery - measurements will be complete within 30 minutes of starting anaesthesia ] [ Designated as safety issue: No ]

Analysis of agreement between Nexfin cardiac output and the calibrated cardiac output measured by LiDCOplus

Bias and limits of agreement for change in cardiac output measured by Nexfin compared with LiDCO [ Time Frame: During anaesthesia period of surgery - measurements will be complete within 30 minutes of starting anaesthesia ] [ Designated as safety issue: No ]

Comparison of relative changes in cardiac output recorded by Nexfin and LiDCO in response to intra-anaesthesia / intra-operative events (fluid administration, drug administration)

Measurement of how much blood the heart pumps may be useful in guiding how much intravenous fluid to give patients during surgery. The current monitors either require special drips (arterial and/or central lines) or a probe inserted into the oesophagus (food pipe) which may limit their use. Newer monitors are available which are completely non-invasive and seem to work well in younger patients. Patients with hip fracture are elderly and frail. The investigators wish to see whether the newer non-invasive monitor works well enough compared to the current monitors in this group of patients. If it does this may allow more of these patients to be monitored in this way.

Detailed Description

The investigators wish to compare the accuracy of the newer, non-invasive monitor (Nexfin) against a more established minimally invasive monitor (LiDCO). The LiDCO has a calibration system which allows the absolute accuracy of the Nexfin to be established.